I admitted in yesterday’s post that I’m ambivalent about continuing to use human astronauts. I fully understand things from the astronauts’ perspective and would even take an opportunity to travel to space in the unlikely event that it’s offered to me, but let’s face it: the main argument in favor of using humans is emotional. It’s important to acknowledge and reward inspiration, but there’s an issue that we science- and space-exploration-lovers must accept.

Robots do it better.

I’m not talking about theoretical work or what usually falls into the category of experiment. I’m talking about simple exploration. Robots can endure cold, heat, and long trips between planets, not to mention a refreshing lack of existential dread over the possibility (indeed probability) that they’ll never come back to Earth.* Even a large, heavy robot is lighter than the equipment necessary to sustain a single human. Robots don’t need to eat, drink, or defecate, and suffer changes in of gravity with far more grace than we do. Robotic spacecraft can maintain orbit around a planet for years on end.

Just think about all the great robotic scientific missions operating right now:

• The Hubble Space Telescope—need I say more?
• The Mars rovers, nicknamed Spirit and Opportunity, were designed to operate for 90 days. That was in 2004. By my watch, they’ve been going a lot longer than 90 days, and still are making discoveries, despite the fact that Spirit has gotten stuck on a rock.
• The Cassini-Huygens mission to Saturn and its moons, which has taught us a lot about the planet, Titan, and Enceladus. From a public outreach point of view, the pictures sent back are truly stunning. (My favorite is this one.)
• The Lunar Reconnaissance Orbiter continues to send back high-resolution images of the Moon’s surface, mapping features never before seen. (Here’s a photo of the Apollo 16 landing site.)
• The Mercury Messenger mission (I love alliteration) is preparing to settle into orbit around the smallest planet (yes, I’m picking a fight with the Pluto lovers out there). Much of Mercury’s surface is still unmapped; Messenger will finish the job, and provide a lot more information about a planet that still holds a lot of mysteries.

This list isn’t exhaustive and doesn’t include great past missions like the Explorer satellite, Voyager probes, the Viking missions, the various Mariner probes, and Galileo—and I’m even being American-centric, which is highly unfair to the ESA, Russian, Japanese, and Indian space probes that have done and continue to do excellent work. (Those of you who know me know I’m not really jingoistic, and of course Cassini is actually a joint US-ESA mission. Science at its best is an international venture, and scientific knowledge is shared by all humanity.)

The arguments in favor of spaceflight by humans are largely emotional; the arguments in favor of robotic space exploration are largely practical. I would love to see sunrise over Jupiter, to set foot on the Moon or Mars, to pilot a craft through the ice plumes of Enceladus… yet we aren’t completely deprived of joy by seeing these images sent back by the best missions. Robotic missions still represent what is best about our ingenuity, and I say praise them.

*Several people I’ve spoken with, including Lisa Pratt and one of my physics colleagues at Randolph-Macon, said they would be willing to take a one-way trip to Mars, which once again I understand fully and might even consider myself under the right conditions.